The Importance of Bit Depth

The Importance of Bit Depth

Each digital file you create (capture or scan) is capable of representing a specific number of colors. This capability, usually referred to as the ‘mode’ or ‘color depth’ of the picture, is expressed in terms of the number of ‘bits’. Most photos these days are created in 24-bit mode. This means that each of the three color channels (Red, Green and Blue) is capable of displaying 256 levels of color (or 8 bits per channel). When the three channels are combined, a 24-bit image can contain a staggering 16.7 million separate tones/hues.

This is a vast amount of colors and would be seemingly more than we could ever need, see or print, but many modern cameras and scanners are now capable of capturing up to 16 bits per channel or ‘high-bit’ capture in either Raw or TIFF file formats. This means that each of the three colors can have as many as 65,536 different levels and the image itself, with all three channels combined, a whopping 281,474,976 million colors (last time I counted!). But why would we need to capture so many colors ?

 

More Colors Equals Better Quality

Most readers would already have a vague feeling that a high-bit file (16 bits per channel) is ‘better’ than a low-bit (8 bits per channel) alternative, but understanding why is critical for ensuring the best quality in your own work. But the image quality also depends on the resolution or number of pixels, if the image is low in quality or resolution, people tend to apply vector conversion to increase the quality of the image. There are also some photo editing methods which help to improve the quality of the images for example clipping path, photo retouching, photo manipulation, and old photo restoration etc.

Importance of Bit Depth

Comparing Bit Depth:

The higher the bit depth of an image the more levels of tone and number of colors it can display.

Here are the main advantages in a nutshell:

  1. Capturing images in high-bit mode provides a larger number of colors for your camera or scanner to construct your image. This in turn leads to better color and tone in the digital version of the continuous tone original.
  2. Global editing and enhancement changes made to a high-bit file will always yield a better quality result than when the same changes are applied to a low-bit image.
  3. Major enhancement of the shadow and highlight areas in a high-bit image is less likely to produce posturized tones than if the same actions were applied to a low-bit version.
  4. More gradual changes and subtle variations are possible when adjusting the tones of a high-bit photograph, using tools like Levels, than is possible with low-bit images.
Importance of bit depth
Redistributing the tones on an 8 bits per channel file (2) can lead to loss of levels of gray (white spikes) and noticeable ‘banding’ in the image. 16 bits per channel files (1), by contrast, maintain their appearance of continuous tone even after quite drastic editing and enhancement actions.

 

The Quality Factors of Digital Photograph

The Digital Photograph

Computers are amazing machines. Their strength is in being able to perform millions of mathematical calculations per second. To apply this ability to working with images, we must start with a description of pictures that the computer can understand.

This means that the images must be in a digital form. This is quite different from the way our eye, or any film-based camera, sees the world. With film, for example, we record pictures as a series of ‘continuous tones’ that blend seamlessly with each other. To make a version of the image that the computer can use, these tones need to be converted to a digital form.

The process involves sampling the image at regular intervals and assigning a specific color and brightness to each sample. In this way, a grid of colors and tones is created which, when viewed from a distance, will appear like the original image or scene. Each individual grid section is called a picture element, or pixel.

There are several post production processing for digital photography, such as Clipping Path, Photo Retouching, Photo Manipulation, Image Masking, Color Correction, Vector Conversion and Ghost Mannequin etc. We will discuss all about this photo editing services in our upcoming blogs.

Creating Digital Photos

Digital files can be created by taking pictures with a digital camera or by using a scanner to convert existing prints or negatives into pixel form. Most digital cameras have a grid of sensors, called charge-coupled devices (CCDs), in the place where traditional cameras would have film. Each sensor measures the brightness and color of the light that hits it. When the values from all sensors are collected and collated, a digital picture results.

Scanners work in a similar way, except that these devices use rows of CCD sensors that move slowly over the original, sampling the picture as they go. Generally, different scanners are needed for converting film and print originals; however, some companies are now making products that can be used for both.

Digital Photograph is made up of pixels.
A digital picture is made up of a grid of picture elements or pixels.

Video cameras use the same principle but rapidly capture a sequence of images. Any movement in the subject is recorded on successive photos. When these images, or frames, are quickly re-displayed one after another, the motion of the subject is replicated on screen. Until recently, capturing digital video required a separate camera, now, many still cameras also contain a very usable video mode.

Photo Conversion
Photographs and negatives, or slides, are converted to digital pictures using either film or flatbed scanners.

Quality Factors in a Digital Image

The quality of the digital file is largely determined by two factors – the number of pixels and the number and accuracy of the colors that make up the image. The number of pixels in a picture is represented in two ways – the dimensions, i.e. ‘the image is 900 × 1200 pixels’, or the total pixels contained in the image, i.e. ‘it is a 3.4 megapixel picture’.
Generally, a file with a large number of pixels will produce a better quality image overall and provide the basis for making larger prints than a picture that contains few pixels. The second quality consideration is the total number of colors that can be recorded in the file. This value is usually referred to as the ‘color or bit depth’ of the image.

Size of Digital Image
The size of a digital image is measured in pixels. Images with large pixel dimensions are capable of producing big prints and are generally better quality.

The current standard is known as 24-bit color or 8 bits per Red, Green and Blue channel. A picture with this depth is made up of a selection of a possible 16.7 million colors. In practice this is the minimum number of colors needed for an image to appear photographic. In the early years of digital imaging, 256 colors (8 bits of color per channel) were considered the standard.

Although good for the time, the color quality of this type of image is generally unacceptable nowadays. In fact, new camera and scanner models are now capable of 12 bits per channel (36-bit color altogether) or even 16 bits per channel (48-bit color altogether). This larger bit depth helps to ensure greater color and tonal accuracy.

The Steps in the Digital Process

The Steps in the Digital Process

The Steps in the Digital Process

The digital imaging process contains three separate steps – capture, manipulate and output. Capturing the image is the first step. It is at this point that the color, quality and detail of your image will be determined. Careful adjustment of either the camera or scanner settings will help ensure that your images contain as much of the original’s information as possible. In particular, you should ensure that delicate highlight and shadow details are evident in the final image.
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